Floating agitator



Feb. 6, 1968 J. D. HOWELL 3,367,126-

FLOATING AG ITATOR Filed May 19, 1966 Ill/f L\ V v INVENTOR:

JOHN DONOHOE HOWELL United States Patent Ofiice 3,367,126 FLOATINGAGITATOR John D. Howell, 140 Red Hill Road, New City, N.Y. 10956 FiledMay 19, 1966, Set. No. 551,252 3 Claims. (Cl. 62123) ABSTRACT OF THEDISCLOSURE A tubular crystallizer for solutions having an agitatorshaft, an agitator means and a mounting means which are substantiallythe same weight per unit of length as th weight of solution displaced bythem.

This invention relates in general to freeze concentration, and, moreparticularly, to tubular crystallizers.

A tubular crystallizer has one or more elongated tubes passing through atank of refrigerant. A solution to have crystals formed in it is passedthrough the tube so that crystals may form within the crystallizer tubeas heat is transferred therethrough. To prevent crystal buildup on thetube walls, an agitator shaft extends through the crystallizer tube andhas longitudinal blades mounted thereon to extend with slight clearancetoward the walls of the tube. Oscillatory or rotary motion of theagitator shaft and its blades prevents crystals from forming on thecrystallizer tube wall or removes them from the wall to promote uniformcrystal growth.

For eflicient and greater capacity operation of such crystallizers, thelength of the crystallizer tube is an important factor. Heretofore, tubelengths over ten feet were costly and difiicult to build, as highbending moments were present in long agitator shafts with the resultthat shaft alignment in the tubes was difficult. stiffening of theagitator shafts rendered them heavy and costly. In some applications,bearing shoes to slide on the inner side of the tube walls were providedto support the length of the shafts, but these shoes prevented crystalgrowth in the area over which they slid and they gave rise to problemsof wear, lubrication, etc. Although for some extremely long crystallizertubes embodying the concept of this invention some intermediate bearingmeans may be needed, this invention greatly reduces the requirement forsuch intermediate bearings.

It is, therefore, an object of this invention to provide an agitator orscraper rotor for a tubular crystallizer or the like which is moreeasily aligned and less subject to bending while in operation.

Another object of this invention is to provide an agitator shaft for atubular crystallizer which is less costly to fabricate.

A further object of this invention is to provide an agitator rotor orshaft for a tubular crystallizer which has relatively thin walls whichare internally pressurized to prevent collapse in service.

Still another object of this invention is to provide an agitator shaftassembly for a tubular crystallizer, which is of substantially the samespecific gravity as water, to float within a crystallizer tube.

Yet another object of this invention is to provide an agitator shaftassembly for a tubular crystallizer which greatily reduces the bearingloads of the shaft while it is in service.

Many other objects, advantages, and features of invention reside in theconstruction, combination, and arrangement of parts involved in theembodiment of this invention and its practice otherwise as may beunderstood from the following description and accompanying drawingwherein:

FIGURE -1 is a longitudinal, vertical section through a single tubecrystallizer according to this invention;

FIGURE '2 is a transverse vertical section taken on line 2-2 of FIGURE1; and

FIGURE 3 is a section taken on line 33 of FIGURE 2 showing one possibleform of blade mounting.

Referring to the drawing in detail, a tank 10 has a suitable refrigerantintroduced into it through pipe 11 and exhausted through pipe 12. Weldedor otherwise fixed within tank 10 is a crystallizer tube 13.Crystallizer tube 13 may extend beyond the end walls 14 and 15 of tank10 for ease of manifolding. The arrangement shown is merely oneillustrative example of a tubular crystallizer. Generally, tank 10 wouldhave a plurality of tubes 13 within it to increase its capacity with aneconomy of space.

A hollow agitator shaft 20 has an end shaft 21 projecting from one endto be journalled in a bearing 22 fixed over end wall 15 by bolts 23. Adrive shaft 24 extends from the other end of shaft 20 to pass throughand be journalled in end cap 25 fixed over end wall 14 by means of bolts26. A suitable pack-ing 27 prevents fluid leakage around shaft 24. Asprocket 28 is mounted on shaft 24 to drive agitator shaft 20. V

A number of studs 30 are Welded to shaft 20 at intervals along itslength. Agitator blades 31 are fixed to the studs 30 by means of themounting brackets 32 so that the blades 31 are held a spaced distanceaway from shaft 20 with a slight clearance from the inner surface ofcrystallizer tube 13.

As shown in FIGURE 3, a mounting bracket 32 is slipped over a stud 30and fixed to it by means of a threaded locking element 33. The blades 31may contain laterally elongated apertures allowing the elements 33passage therethrough. Each blade 31 is then positioned on a row ofmounting brackets 32 and held in place by means of blind nuts 34 whichare turned down over the ends of the projecting elements 33. When allthe blades 31 are thus properly positioned, the blades 31 and thebrackets 32 are drilled and tapped to receive the bolts 35 to fix theblades 31 permanently in place. Should it be necessary to adjust thepositions of the blades 31 after lengthy service, the nuts 34 may beremoved and the elements 33 unscrewed so that the brackets 32 may berepositioned along the studs 30.

While four blades 31 are shown, any desired number may be used. Materialto be crystallized is introduced through tube 40 and withdrawn throughtube 41. The agitator shaft 20, the blades 31, the brackets 32, and allassociated elements are best made of stainless steel for mostapplications.

As one example of this invention, an agitator shaft 20 thirteen feetlong was made of five inch inside diameter pipe, schedule 10, in type316 stainless steel. This pipe weighed 7.65 pounds per foot. Four blades31 and fittings Weighed 2.2 pounds per foot. Thus total weight per footwas about 9.85 pounds per foot. Buoyancy was about 10.7 pounds per foot.Thus all consideration due to weight when operated in a water solutionwas eliminated. If heavier schedule 40 five inch inside diameter pipehad been used, it alone would have weighed 14.62 pounds per foot and theassembly would have been 6.12 pounds per foot heavy in a water solutionto introduce bending moments.

Further to stiffen the relatively thin walled schedule 10 pipecrystallizer shaft 20 and prevent it from collapsing in service, it maybe internally pressurized, for example, to 100 pounds per square inch,with air or a suitable gas through a small channel 44 as shown inFIGURE 1. Channel 44 may then be sealed by a threaded plug or the like.When the crystallizer operates near freezing or below, the internalpressure will still be over pounds per square inch above atmosphericpressure. The use of Patented Feb. 6, 1968 the thinner walled pipe infabricating shafts 20 results ina-considerable' saving in materialcosts. Further, the foregoing example is not to be construed to limitthe scope of this invention which may be scaled to any crystallizerapplication.

While this invention has been shown and described in the best formknown, it will nevertheless be understood that this is purely exemplaryand that modifications may be made without departing from the spirit andscope of the invention.

What is claimed is:

1. In a tubular crystallizer for solutions, having a tank,-

means introducing a refrigerant into said tank, at least one elongatedcrystallizer tube passing through said tank, means introducing asolution into one end of said tube to pass through said tube, meanswithdrawing a solution and crystal slurry from the other end of saidtube, wherein an agitator assembly comprises, in combination, an agi-,

tator shaft within said tube, bearing means at least at the ends of saidshaft rotatably mounting said shaft within said tube, longitudinalagitator means, means mounting said agitator means a spaced distanceaway from said agitator shaft adjacent to said tube, and means drivingsaid agitator shaft, said agitator shaft being hollow, the improvementin which said agitator shaft, said agitator means, and said mountingmeans are substantially the same weight per unit of length asthe weightof solution displaced by said agitator shaft, said agitator means, andsaid mounting means per unit of length.

2. The combination according to claim 1 wherein said agitator shaft istubular and rounded in section.

3. In a tubular crystallizer for solutions having a tank, meansintroducing a refrigerant into said tank, at least one elongatedcrystallizer tube passing through said tank, means introducing asolution into one end of said tube to pass through said tube, meanswithdrawing a solution and crystal slurry from the other end of saidtube, wherein an agitator assembly comprises, in combination, anagitator shaft within said tube, bearing means at least at the ends ofsaid shaft rotatably mounting said shaft within said tube, longitudinalagitator means, means mounting said agitator means a spaced distanceaway from said agitator shaft adjacent to said tube, and means drivingsaid agitator shaft, said agitator shaft being hollow, saidagitatorshaft, said agitator means, and said mounting means beingsubstantially the same weight per unit of length as the weight ofsolution displaced by said agitator shaft, said agitator means, and saidmounting means per unit of length, the improvement which includes gasunder pressure within said hollow tubular agitator shaft.

References Cited UNITED STATES PATENTS 2,267,081 12/1941 Crighton 165942,745,261 5/ 1956 Merrill 62342 3,264,836 9/1966 Miller et al 62342 XLLOYD L. KING, Primary Examiner.

ROBERT A. OLEARY, Examiner.

W. E. WAYNER, Assistant Examiner.

